The subject of the present invention is novel fluorocopolymers and their use for the coating and the impregnation of various substrates, such as textiles, leather, wood, non-wovens, metal, concrete, stone and, more particularly, paper and similar articles, for the purpose of making them oleophobic and hydrophobic. The invention also relates to the substrates thus treated.
To achieve this objective, many fluoroderivatives have already been proposed.
International Application WO 98/23657 thus teaches cationic fluorocopolymers capable of being obtained by the copolymerization of:
52 to 92% by weight of one or more polyfluoromonomers of general formula: 
in which Rf represents a perfluorinated radical, having a straight or branched chain, containing 2 to 20 carbon atoms, preferably 4 to 16 carbon atoms, B represents a divalent linking which is linked to O by a carbon atom and which may comprise one or more oxygen, sulphur and/or nitrogen atoms, one of the symbols R represents a hydrogen atom and the other a hydrogen atom or an alkyl radical containing 1 to 4 carbon atoms;
1 to 25% of one or more monomers of general formula: 
in which Bxe2x80x2 represents a linear or branched alkylene radical containing 1 to 4 carbon atoms, Rxe2x80x2 represents a hydrogen atom or an alkyl radical containing 1 to 4 carbon atoms, the symbols R1 and R2, which are identical or different, each represent a hydrogen atom, a linear or branched alkyl radical containing 1 to 18 carbon atoms or a hydroxyethyl or benzyl radical, or R1 and R2 together with the nitrogen atom to which they are linked form a morpholino, piperidino or pyrrolidin-1-yl radical;
1 to 25% of a vinyl derivative of general formula:
Rxe2x80x3xe2x80x94CHxe2x95x90CH2 
in which Rxe2x80x3 may be an alkyl carboxylate or alkyl ether group containing from 1 to 18 carbon atoms.
The copolymerization reaction leading to the fluorocopolymers described by that international application is carried out in solution in a water-miscible organic solvent or solvent mixture and is followed by a step of dilution with an aqueous solution of a mineral or organic acid. This dilution step is carried out in the presence of hydrogen peroxide or is followed by a treatment by means of an aqueous hydrogen peroxide solution.
After the said dilution step, it is necessary to carry out a vacuum distillation or to flush with an inert gas, for example nitrogen, in order to remove the volatile compounds and to obtain a composition that can be sold and applied to the substrate to be treated.
The solvents exemplified in that application are, mostly, mixtures based on N-methylpyrrolidone. Because of their boiling point, these solvents are not completely removed by the distillation operation so that significant quantities of them remain in the commercial composition.
This commercial composition is thus in the form of a solution, thereby giving it stability properties which are highly advantageous for its transportation and its storage.
However, for some applications, and especially for the treatment of papers or similar articles intended for the field of packaging food products, it is desirable to reduce the amount of any solvents in commercial compositions, or even to completely eliminate them therefrom.
International Application WO 98/23657 mentions (cf. page 5 lines 14-15) that the use of light solvents makes it possible to obtain, after distillation, a commercial composition containing no organic solvent.
However, during the operation of distilling these light solvents, a gradual precipitation of the cationic fluorocopolymers occurs, which then results in an unstable aqueous dispersion, i.e. one which results in a settling in a few hours. Such a dispersion is unsuitable as a commercializable composition.
It has now been found that the introduction of an anionic monomer, or a monomer which is potentially anionic by varying the pH, into the copolymers described by the international application, and a modification to their synthesis process, makes it possible to obtain novel fluorocopolymers which confer on various substrates, and especially on paper, the same hydrophobic and oleophobic properties and which, in addition, may be in the form of aqueous compositions which contain no organic solvents and are stable over time.
Fluorocopolymers according to the present invention are obtained by polymerization of a monomer mixture comprising by weight:
(a) from 50 to 92%, preferably from 70 to 90%, of one or more polyfluoromonomers of general formula: 
in which:
Rf represents a perfluorinated radical having a straight or branched chain, containing 2 to 20 carbon atoms, preferably 4 to 16 carbon atoms,
B represents a divalent linking which is linked to O by a carbon atom and which may comprise one or more oxygen, sulphur and/or nitrogen atoms,
one of the symbols R represents a hydrogen atom and the other a hydrogen atom or an alkyl radical containing 1 to 4 carbon atoms;
(b) from 1 to 25%, preferably from 8 to 18%, of one or more monomers of general formula: 
in which:
Bxe2x80x2 represents a linear or branched alkylene radical containing 1 to 4 carbon atoms,
Rxe2x80x2 represents a hydrogen atom or an alkyl radical containing 1 to 4 carbon atoms,
the symbols R1 and R2, which are identical or different, each represent a hydrogen atom, a linear or branched alkyl radical containing 1 to 18 carbon atoms or a hydroxyethyl or benzyl radical, or R1 and R2 together with the nitrogen atom to which they are linked form a morpholino, piperidino or pyrrolidin-1-yl radical;
(c) from 0.5 to 20%, preferably from 1 to 10%, of an anionic monomer or a monomer which is potentially anionic by varying the pH (III), such as alkene carboxylic acids, monoolefinic derivatives of sulphonic acid, and their salts of alkali or alkaline-earth metals;
(d) from 2 to 10% of a vinyl derivative of general formula:
Rxe2x80x3xe2x80x94CHxe2x95x90CH2xe2x80x83xe2x80x83(IV) 
in which Rxe2x80x3 may be an alkyl carboxylate or alkyl ether group containing from 1 to 18 carbon atoms;
(e) from 0 to 10%, preferably from 0 to 8%, of any monomer other than the monomers of formulae I, II, III and IV;
With regard to monomer (c), mention may be made especially of (meth)acrylic acid as an example of an alkene carboxylic acid and acrylamidomethyl-propanesulphonic acid as an example of a monoolefinic derivative of sulphonic acid.
The fluorocopolymers according to the present invention are prepared by copolymerization of the monomers in solution in a distillable organic solvent. The term xe2x80x9cdistillablexe2x80x9d solvent is understood to mean any organic solvent or solvent mixture whose boiling point at atmospheric pressure is less than 150xc2x0 C. Next, the reaction mixture is diluted with water in the presence of a mineral or organic acid in order to salify the macromolecules.
According to a preferred variant of the invention, this dilution step is carried out in the presence of hydrogen peroxide or is followed by a treatment by means of an aqueous hydrogen peroxide solution.
These fluorocopolymers can be applied to various substrates, such as leather, non-wovens, building materials, paper and board. In particular, they can be applied to paper using various techniques (applied in a size press or applied in the bulk), thus giving the paper, without the need for additives (sequestrants, retention agents, fixing resins, etc.), excellent hydrophobic and oleophobic properties.
According to the present invention, it is preferred to use:
(a) as polyfluoromonomers of formula I, the compounds of formula: 
in which RF is a perfluoroalkyl radical containing 4 to 16 carbon atoms;
(b) dimethylaminoethyl methacrylate or N-tert-butylaminoethyl methacrylate as monomer of formula II;
(c) methacrylic acid as monomer of formula III; and
(d) vinyl acetate as monomer of formula IV.
As distillable organic solvent in which the copolymerization is carried out, mention may be made by way of non-limiting example of ketones (for example acetone or methyl ethyl ketone), of alcohols (for example isopropanol) and of ethers (for example THF or dioxane).
For implementing the invention, it is preferred to use, as solvent, methyl isobutyl ketone (MIBK) or methyl ethyl ketone (MEK) or a mixture of these with acetone.
The total concentration of monomers in the organic solvent or solvent mixture may range from 20 to 70% by weight and is preferably between 40 and 60%.
The copolymerization is carried out in the presence of at least one initiator, used in an amount from 0.1 to 2% with respect to the total weight of monomers. As initiators, it is possible to use peroxides such as benzoyl peroxide, lauroyl peroxide, succinyl peroxide and tert-butyl perpivalate, or azo compounds such as, for example, 2,2xe2x80x2-azobis(isobutyronitrile), 4,4,xe2x80x2-azobis(4-cyanopentanoic acid). The copolymerization step may be carried out at a temperature ranging from 40xc2x0 C. up to the boiling point of the reaction mixture. It is preferably carried out at between 60 and 90xc2x0 C.
The dilution step consists in adding an aqueous solution of a strong or moderately strong mineral or organic acid, that is to say an acid whose dissociation constant or whose first dissociation constant is greater than 10xe2x88x925, to the organic solution of the copolymer.
As examples of such acids, mention may be made of hydrochloric, hydrobromic, sulphuric, nitric, phosphoric, acetic, formic, propionic and lactic acids, but it is preferred to use acetic acid. The amount of aqueous solution to be used and its acid concentration must be sufficient, on the one hand, to completely salify the amine functional groups provided by the monomer(s) of formula II and, on the other hand, to obtain a final copolymer solution having a solids content of between 5 and 30%, preferably between 20 and 30%. In order to completely salify the amine functional groups, the amount of acid is advantageously between 0 and 5 acid equivalents, preferably between 1 and 2 equivalents, with respect to the monomer(s) of formula II.
The amount of hydrogen peroxide used is between 0 and 10%, preferably between 0.5 and 4%, with respect to the total initial weight of monomers. The treatment is carried out at between 25 and 100xc2x0 C., preferably at between 70 and 85xc2x0 C.
The subject of the present invention is also the aqueous compositions comprising a fluorocopolymer as defined above. The said compositions are obtained by completing the process for manufacturing the fluorocopolymer as defined above with a distillation step, so as to remove any trace of organic synthesis solvent. The aqueous compositions obtained therefore do not have a flashpoint between 0 and 100xc2x0 C. according to the ASTM D3828 standard. The distillation may be carried out at atmospheric pressure or reduced pressure. In general, these aqueous compositions are in the form of dispersions which are stable over time. Thus, these dispersions remain homogeneous and can therefore be transported and stored while still remaining capable of being used for the hydrophobic and oleophobic treatment of substrates. Advantageously, they are also water-dilutable.
The concentration of fluorocopolymer according to the invention in water is generally between 1 and 50%, preferably between 20 and 30%.
The subject of the present invention is also a solid substrate comprising at least one fluorocopolymer according to the invention, as defined above.
As substrates capable of being made oleophobic and hydrophobic with the products according to the invention, it is preferred to use paper, board and similar materials. It is also possible to use other highly varied materials such as, for example, woven or non-woven articles based on cellulose or regenerated cellulose, on natural, artificial or synthetic fibres such as cotton, cellulose acetate, wool, silk, polyamide, polyester, polyolefin, polyurethane or polyacrylonitrile fibres, leather, plastics, glass, wood, metals, porcelain and painted surfaces. It may also be advantageous to treat building materials such as concrete, stone, brick and tiles with the products according to the invention.
The aqueous compositions comprising a fluorocopolymer according to the invention are mainly applied diluted in an aqueous medium using known techniques, for example by coating, impregnation, immersion, spraying, brushing, padding or film-coating.
The products according to the invention can be applied in aqueous solution to paper, either onto the surface of the already completed substrate (preferably in an amount of 0.05 to 0.2% fluorine with respect to the weight of paper) or into the body of the material, that is to say into the paper pulp (preferably in an amount of 0.2 to 0.4% fluorine with respect to the weight of pulp).
The substrates thus treated exhibit good oleophobic and hyrophobic properties after simple drying at room temperature or at high temperature, optionally followed by a heat treatment which can range, depending on the nature of the substrate, up to 200xc2x0 C.
To obtain good attachment of the fluorocopolymers according to the invention to the substrates to which they have been applied, and, in addition, to confer a specific effect, it is sometimes advantageous to combine them with certain additives, polymers, thermocondensable products and catalysts capable of promoting their crosslinking with the substrate. Mention may be made, as such, of urea-formaldehyde or melamine-formaldehyde condensates or precondensates, epoxy derivates, such as diglycidylglycerol, polyamine-epichlorohydrin resins, glyoxal and its derivates, polyvinyl alcohols and cationic, oxidized and amphoteric starches.
It may also be advantageous to combine the fluorocopolymers according to the invention with one or more nonionic and/or cationic surfactants in order to improve the wetting of the substrate. The weight of this or these surfactants with respect to the total weight of copolymer may vary from 0 to 100%.
The surfactants may be added to the organic solution during the copolymerization reaction, during the dilution or to the aqueous composition obtained after distilling off the solvent. They may also be added at the time of application of the copolymers according to the invention.
The following tests were used to evaluate the performance of the treated substrates according to the invention: